Sealing caps of this kind for cosmetic applicators, which are composed of a tubular cap body whose interior is divided into two regions by a plate to which is attached a wand or shaft that in turn holds the actual applicator, are widely used in the cosmetics industry.
As a rule, the plate also performs the task of providing a sealing surface, which, when the sealing cap is completely closed, is pressed against the bottle neck or against the rim of the stripper protruding from this neck, in order to reliably seal the cosmetic receptacle.
In order to be able to exert the sealing pressure required for this as conveniently as possible, the cap body is provided, usually on its inner circumferential surface, with a thread profile that protrudes relatively far in the radial direction into the open space encompassed by the cap body. The thread profile constitutes a holding projection: with the aid of this thread profile, the sealing cap can be screwed onto a receptacle provided with a complementary thread groove until the plate rests with the pressure required for a reliable seal against the end surface of the receptacle neck or the stripper that encompasses this end surface.
It has, however, long been known that the thread stands in the way of a truly efficient manufacture of the sealing cap. The problem is that as a rule, these sealing caps are manufactured by means of injection molding. To this end, an injection mold is used, which is composed of two parts, between which is formed the mold cavity that produces the sealing cap. To remove the completed injection molded sealing cap from the mold, the two mold halves are pulled apart from each other in the direction parallel to the longitudinal axis of the sealing cap. However, the sealing cap is not yet completely free, even when the two mold halves are pulled all the way apart from each other. Instead, it remains attached at first to the mold half that provides the core that has produced the internal thread on the inner circumference of the cap body. In order to remove the sealing cap, it must then be unscrewed from this core in a subsequent work step. Since this problem has already existed for a long time, corresponding robots have already long ago been developed, which perform this unscrewing in a fully automated fashion. Nevertheless, the necessity for such an unscrewing increases the cycle time and necessarily incurs an additional equipment expense.
A similar problem arises in the manufacture of a sealing cap that does not in fact have a thread profile, but instead has a bayonet closure. Such a closure likewise functions with a holding projection that protrudes relatively far in the radial direction into the open space encompassed by the cap body.
In the low-budget sector, therefore, sealing caps are consistently used, which instead of an internal thread, use an elastic detent bead, which does indeed also protrude inward, but only so slightly that the sealing cap, with the aid of the linear movement of a correspondingly strong ejector, can be slid downward by the core that forms the detent mechanism, because it can expand elastically enough for the detent bead to be pulled out of the recess in the mold in which it has been formed. Such detent closures often do not remain really leak-proof over the long term since with the aid of such a detent closure, it is difficult over the long term to exert relatively powerful forces that act in the direction of the longitudinal axis L and prestress the sealing surfaces against each other with sufficient force.
In light of this, the object of the invention is to create a sealing cap that can be efficiently manufactured, even though it is provided with a holding projection that protrudes farther in the radial direction into the open space encompassed by the cap body than a mere detent bead.